Communication method and system for aggregates of separate entities using data/management path and mapping path for identifying entities and managing a communication network

ABSTRACT

A system and method for communication and management of an aggregate is provided including a plurality of separate entities, each entity residing in a separate environment. The system includes a data path which is provided as a common medium. Each of the entities is connected to the data path for exciting the medium with a signal. All entities connected to the common medium receive the signal. A mapping path is also provided. The mapping path is implemented as a multitude of point-to-point connections such that each entity is connected directly to another entity via a point-to-point connection or connected to a first entity by a point-to-point connection and connected to a second entity by a point-to-point connection. The connections provide a known topology, allowing identification of all entities adjacent to a given entity to establish mapped adjacent entities. From these mapped adjacent entities all entities adjacent to the mapped adjacent entities are mapped until all entities of the aggregate are mapped.

FIELD OF THE INVENTION

The invention relates to the field of communications in general and moreparticularly to communication involving networks such as local areanetworks, wide area networks and the like wherein entities provideservices to one or more users including providing a connection to otherentities which are coupled to other users. The entities with which theinvention relates reside in separate environments (for example, but notlimited to, separate enclosures). The entities may be assembled togetherin order to implement a unified aggregate which provides a service andthe aggregate can communicate with a management agent (human orelectro-mechanical) as a whole.

BACKGROUND OF THE INVENTION

It is known in the field of local area networks to provide bridges,routers and hubs and other entities which provide a connective functionand provide other functions to users of the network. Hubs typicallyprovide a connection platform whereby various individual users areconnected through the hub to users connected to other hubs (for exampleat other locations or at the same location). It is known in the art toprovide hubs (also referred to as concentrators herein) which provide abackplane allowing communication between different users connected tothe concentrator. Often, there is a need for an additional concentratorat the same location, typically due to the fact that all of theconnection locations of the concentrator have been used. Typically, thehubs are connected in a method which is known as daisy chaining whereinconnection ports are used to chain hubs together thereby providing amultiplicity of the connection sites, based on the number of hubsprovided. For example, if each hub has eight ports, and the hubs aredaisy chained together, at least one port out of 8 is used for daisychaining. With three hubs daisy chained together, the center hub willhouse 6 free ports, i.e. 20 total connection ports are provided at thesingle location wherein 3 hubs are used.

Networks are known wherein a management agent is provided for overseeingthe network. The agent manages communications between users connected atpoints of access. Such management can include setting up one or morenetworks by either physical or logical connection of points of accessand also monitoring the network including monitoring activity such asmonitoring collisions and monitoring connections. In situations whereina plurality of entities are provided in separate environments (such as,but not limited to separate enclosures) and the entities are assembledtogether or connected together in order to implement a unified aggregatewhich provides a service, it is still desirable to provide a managementagent (human or mechanical) for the aggregate.

SUMMARY AND OBJECTS OF THE INVENTION

It is an object of the invention to provide a communication andmanagement method and system based on entities which reside in separateenvironments (for example, within separate enclosures) wherein theentities are assembled together in order to implement a unifiedaggregate which provides a service and wherein the aggregate cancommunicate with a management agent (human or mechanical) as a whole.

According to the invention, a system for communication and management ofan aggregate based on separate entities is provided including aplurality of separate entities, each entity residing in a separateenvironment. This system includes a data path which is provided as acommon medium. Each of the entities is connected to the data path forexciting the medium with a signal. All entities connected to the commonmedium receive the signal. A mapping path is also provided. The mappingpath is implemented as a multitude of point-to-point connections suchthat each entity is connected directly to another entity via apoint-to-point connection or connected to a first entity by apoint-to-point connection and connected to a second entity by apoint-to-point connection. The connections provide a known topology,allowing identification of all entities adjacent to a given entity toestablish mapped adjacent entities and from said mapped adjacententities to establish all entities adjacent to said mapped adjacententities until all entities of the aggregate are mapped.

The management agent can be provided as software wherein the managementagent is connected to the aggregate via one or more active points ofaccess residing in one or more of the entities. For example, networkmanagement software may be present in a computer which is connected toone or more of the entities. The management agent manages communicationson the data path including storing necessary data.

The system includes a procedure for providing one of the entities as acoordinating entity, wherein the coordinating entity provides a point ofaccess for the managing agent. Several of the entities may have theability to provide the point of access to the management agent and eachof these entities includes designation means for participating in aprocess for designating a coordinating entity.

The designation means may be in the form of an intelligent device suchas a processor, located in the entity, wherein the algorithm andprocedure is followed based on software/hardware present in the entity.The entity may also be somewhat passive and the software or hardwarestructure (means) for designation is connected to the entity (such ascomputer units connected to the entity). The provision of means in anentity (both hardware and algorithms implemented in software INSIDE theentity) is preferred. According to this preferred embodiment, theentities in the aggregate are of two kinds:

1) Those which contain software (S/W) and/or hardware (H/W) capable tomonitor and manage the aggregate.

2) Those which DO NOT contain S/W and/or H/W capable to monitor andmanage the aggregate.

For example, according to the preferred system of the invention, baseunit(s) and expansion unit(s) are provided. Only the base unitsparticipate in the designation process. The base units are of the kindnoted as 1 above. Once one unit is designated it will actively monitorthe units in the aggregate, and upon certain conditions take steps toinduce changes in the operation and functionality of the other entitiesin the aggregate.

The designation means listens to the data path medium for apredetermined period of time for detecting communication signals. Upondetecting communication signals, the designation means awaits issuanceof a message from the coordinating entity. The message requests that allunmapped entities signal their presence for mapping. If no communicationsignalling is detected on the data path, the designation means transmitsa signal containing unique information identifying itself. If duringthis transmission of unique information identifying itself additionalentities transmit their unique information identifying themselves, thedesignation means of each of the entities ends their transmission andthe designation means of each entity randomly chooses a time period.Upon expiration of the randomly chosen time period, the designationmeans of each entity will attempt to transmit again its uniqueinformation identifying itself. The entity which completes thetransmission of the unique information is established as thecoordinating entity.

The coordinating entity coordinates all communications on the data pathincluding sending a message addressed to an entity in the aggregatewhereby the entity receives the message from the coordinating entity,performs the necessary operations and transmits a message containinginformation relevant to the received message. With this system, thecoordinating entity addresses each entity in the aggregate within aspecified and agreed upon time period. The designating means of eachentity listens to the data path medium for the predetermined period oftime. If it does not detect any communication signals, it can eitherisolate itself to operate as a stand-alone entity independent of theaggregate, initiate the algorithm for designating the entity as thecoordinating entity or it can wait for the coordinating entity to issuea request that all unmapped entities send a message announcing that theyare connected to the aggregate.

The mapping path of the system of the invention is independent of thedata path which allows two entities in the aggregate to communicatesimultaneously, namely along the data path and along the mapping path.The topology of the mapping path is preset or known and this may be, forexample, a ring. The topology may be other known topologies, however,the mapping path is preferably based on point-to-point connection,between entities adjacent to each other. For example, a stack ofentities may be provided wherein each entity is connected to an entityabove it and below it, or in the case of the top entity, the entity isconnected by point-to-point connection to the entity immediately belowand also to the bottom-most entity (to form a simple ring). A mappingpath can also be implemented by multiplexing, including spatialmultiplexing or multiplexing based on different frequency ranges.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1a is a schematic representation of the aggregate formed ofseparate entities according to the invention;

FIG. 1b is a schematic view of elements of an entity which can act ascoordinating entity.

FIG. 2 is a logical flow path describing the situation for entities ofthe aggregate during power-up and the steady state functionality of theaggregate;

FIG. 3 is a flow chart describing the designation of a communicationcoordinator;

FIG. 4 is a logical flow chart for a non-manager entity;

FIG. 5 is a logical flow chart for an active manager;

FIGS. 6 and 7 are logical flow charts describing the process of mappingthe aggregate based on a preferred topology wherein entities areconnected in a circle as shown in FIG. 1;

FIG. 8 is a circuit diagram showing a collision mechanism which isimplemented on the data path;

FIG. 9 is a front view showing an embodiment of the invention based onentities which are concentrators connected by patch cables;

FIG. 10 is a circuit diagram of the transmit/receive circuitry for thedata path of the system of the invention; and

FIG. 11 is a circuit diagram of the mapping signal generation anddetection circuitry of the system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in particular, the invention comprises anaggregate generally designated 10. The aggregate is formed of aplurality of separate entities 12. Each of the entities 12 resides in aseparate environment. For example, the environment may be in the form ofa separate enclosure 14, within which one entity resides. The entities12 are assembled together in order to implement a unified aggregate 10.The aggregate 10 provides a service and the aggregate 10 can communicatewith a management agent (human or mechanical) as a whole.

The entities 12 are connected to one another via a data path 16. Each ofthe entities is connected to the data path 16 as shown by connection 18.The data path is implemented as a common medium. Each entity 12 isconnected to the data path via connection 18 such that it can excite themedium with a signal which is then received by all of the entitiesconnected to the common medium 16.

The aggregate 10 also includes a mapping path 20 which is implemented asa multitude of point-to-point connections 22. The connections of theentities forms a path with a predetermined topological shape. FIG. 1adepicts a ring topology however the system and method of the inventionare not limited to any specific topology.

Signals on the mapping path 20 are independent of signals on the datapath 16. The mapping path can be implemented by any means ofmultiplexing. For example, multiplexing here is used to include separatephysical connections (spacial multiplexing) or other multiplexingtechniques such as use of different frequency ranges. For example, thedifferent frequency range multiplexing can be implemented by using DCsignaling.

The invention provides that some of the entities (base units) include adesignating means in the form of hardware (a coordinating processor withmemory) and/or software whereby an entity for coordinatingcommunications is designated. Other entities have no designating means.In the embodiment shown in FIG. 9, at least one of the entities (atleast one of the network concentrators 40) is a base unit which containssoftware (S/W) and/or hardware (H/W) capable to monitor and manage theaggregate. The other entities may be either base type units or expansionunits which do not contain S/W and/or H/W capable to monitor and managethe aggregate. The hardware may be a commercially available processorfor executing the algorithms as described herein. Memory is alsopreferably provided. However, the designation means may also be providedin a unit (computer) connected to the entity, allowing the use of theprocessor and memory of the connected computer.

FIG. 1b provides a schematic showing of an entity 12 with CPU 22, memory23, and ports 24. The ports 24 are connected to users, such as over aknown medium including fiber optic cable, coax cable,unshielded/shielded twisted pair etc.. Entities 12 which can bedesignated the coordinating unit or designating entity are provided witha CPU and software for running the coordinating unit designation and themapping as described herein.

According to the invention, the aggregate designates one of the entitiesin the aggregate for coordinating the aggregate. The designation is byuse of an algorithm provided for example through software available ineach designating means of an entity 12 capable of being designated. Thedesignated entity or coordinating entity coordinates the transfer of allmanagement information relevant to the aggregate. Any of the entitieswhich includes the designating means and also which provides one or morepoints of access for a management agent, can be the coordinating entity.As used herein, management agent refers to software or software andhardware wherein the management agent is external to the aggregate. Forexample, such a management agent could be ONdemand® network managementsoftware offered by Chipcom Corporation of Southborough Mass. Suchsoftware may be installed in a computer which is connected to theaggregate, such as through one or more of the entities 12. The aggregate10 provides one or more points of access, residing in one or more of theentities which are members of the aggregate 10. Anyone of the entities12 which is capable of acting as the coordinating entity takes part inthe designating process based on the algorithm as mentioned above. Oneof the entities then becomes the coordinating entity, after thedesignating process. This coordinating entity provides the point ofaccess to the management agent and maintains an information databasewhich is necessary for management purposes. The information database iscompiled by the coordinating entity using its designated status.

The coordinating entity performs its function by sending a messageaddressed to an entity in the aggregate. A receiving entity whichreceives a message from the coordinating entity, addressed to thatreceiving entity, performs all of the operations indicated by thereceived message and transmits a message containing information relevantto the message received. The coordinating entity is required to addresseach entity in the aggregate within a specified and agreed upon timeperiod. If an entity in the aggregate does not receive a message fromthe coordinating entity it will initiate one of the three processes,namely:

Isolate itself, and operate as a stand alone entity independent of theaggregate.

Initiate the algorithm which designates an entity in the aggregate tocoordinate the transfer of information (coordinating entity).

Await for the designated entity to issue a message requesting allun-mapped entities to send a message announcing that they are connectedto the aggregate.

Referring to FIG. 2, upon power-up, several or all of the entities inthe aggregate will execute the top level logical flow paths depicted inFIG. 2. The flow chart describes both the power-up and steady statebehavior of the aggregate.

The aggregate 10 is first powered-up as indicated at step 30. Afterpower-up, all entities which are capable of being designated as thecoordinating entity compete for managership as noted as step 32. Thisprocedure is described with reference to the logical flow path of FIG.3.

As shown in FIG. 3, the process of competition for the managership ineach entity which can be designated begins by a listening period 102. Ifthe entity does not detect any signals on the data path 16, it will senda message comprising a number of bytes, indicating its identity and thefact that it is the coordinating entity 104. At the end of thetransmission period the entity will verify that it received its ownmessage uncorrupted (no collusion occurred) as shown at 106. Anuncorrupted message is considered to indicate that during thetransmission no other entity attempted to transmit a message of its own.A corrupted message indicates collision, that is another entityattempted to transmit a message during the same time. If a collisionoccurred, the entity will choose a random time period 108, during whichit will listen to the data path 16. The entity will wait for the chosentime period 110, and when the chosen time period expires, it will verifyif any message was transmitted on the data path 112. If no messages weretransmitted on the data path 16, the entity will again transmit itsmessage indicating its identity and the fact that it is the coordinatingentity as shown at step 104. If at the expiration of the chosen time theentity detects a received message it will exit the process ofcompetition for the managership as shown at step 116. If the messageindicating the entity's identity and the fact that it is thecoordinating entity 104 is received without corruption the entity willassume the function of coordinator for the aggregate management as notedat step 114.

Upon terminating the process depicted in FIG. 3, if the entity is thecoordinating entity 114, it will perform a mapping of the aggregate asshown at step 36 on FIG. 2. The mapping process uses the coordinatingprocessor and memory and software following an algorithm as depicted inFIG. 7. The designated entity starts the mapping process 500, by issuinga command 501 to all entities in the stack to open the mapping bridges.By opening the bridge, an entity in the aggregate prevents the mappingsignal from propagating along the mapping path 20. The designated entityissues to all entities in the aggregate the command 502 to listen totheir upstream connection on the mapping path 20. The upstream directionis arbitrary but must be uniquely defined for all entities capable ofconnecting into an aggregate. For the purpose of this document upstreamwill be defined as a signal received by an entity on the mapping path 20while propagating clockwise. The designated entity enables its ownreceiver at step 503, listening to the upstream direction. Thedesignated entity begins transmission at step 504 of a mapping signal inthe downstream direction and verifies if a mapping signal is receivedfrom the upstream 505. If no mapping signal is received from theupstream direction by the designated entity, it sends a broadcastcommand at 506 requesting identifying information on the entity in theaggregate which receives the mapping signal. In the specificimplementation described here the chosen topology of the mapping path20, is a circle, guaranteeing that at most one entity will be entitledto provide the requested information. The designated entity verifies atstep 507 if a response message is received. If no message is received atimer is verified. If the time allocated for awaiting an answer has notexpired as noted at step 508, the designated unit continues to wait forthe requested information. Upon reception at step 509 of the requestedinformation, the designated entity, logs it in its mapping data-base.Once a unit in the aggregate is recorded in the data base of thedesignated entity, a command at 510 is issued to it, to close themapping bridge. In doing so, an entity in the aggregate allows themapping signal to propagate to the next downstream entity. Thedesignated entity attempts to map the whole aggregate repeating theprocedure described at steps 505, 506, 507, 508, 509, and 510. Thisprocedure is terminated in one of the two ways:

The designated entity may receive at step 505 a mapping signal from itsupstream neighbor. Since the described mapping topology is a circle,that means that the process has logged all units.

The designated entity may detect at 508 that the waiting time for aresponse has expired. Such an occurrence is possible if one of the pointto point connections along the mapping path 20 is malfunctioning. Insuch a case the designated entity issues a command at 511 to all as ofthat time unmapped entities to listen for a mapping signal coming fromtheir downstream neighbor. Then the designated entity transmits amapping signal at step 512 in the upstream direction, and issues arequest at 513 for information identifying the entity in the aggregatewhich receives the mapping signal. The designated entity verifies if aresponse message is received at 516. If no message is received a timeris verified. If the time allocated for awaiting an answer has notexpired at step 517, the designated unit continues to wait for therequested information. Upon reception of the requested information at515, the designated entity, logs it in its mapping data-base. Once aunit in the aggregate is recorded in the data base of the designatedentity, a command is issued to it, to close the mapping bridge 510. Indoing so, an entity in the aggregate allows the mapping signal topropagate to the next upstream entity. The designated entity attempts tomap the whole aggregate repeating the procedure described in 513, 514,515, and 517. This procedure continues until the wait time verified in517 expires without a response from an entity in the aggregate.

Following the completion of the aggregate mapping, the designated entityverifies if it is expected to act as the active manager at step 37 (FIG.2). If the result of the verification is yes, the designated entityenters the active manager program 38 in FIG. 2. The detailed program forthe active manager is described with reference to FIG. 5.

The activity of the active manager (of the coordinating entity) is acontinuous cycle which poles the units in the aggregate, and takes placeon the data path 16, only. The cycle arbitrarily starts by addressingthe first downstream entity at step 300. If the sent message was arequest 301 for an action or for obtaining information, the activemanager adds the request content 302 and verifies that the message hasbeen received by itself corrupted 303. If the message was not receivedby the active manager, it is transmitted again. If the transmittedmessage is not corrupted, the active manager waits for a period of timeas noted at step 304, to receive the requested answer at 305. If thewaiting time at 306 expires without a response from the addressedentity, the entity which did not respond is removed from the mappingdata base at 307. If a response is received on time as per step 306 theinformation is recorded and the next entity in the aggregate isaddressed at 308. If not all entities in the aggregate are addressed, atstep 309, the process continues to 301 and repeats. If all units in theaggregates have been addressed at step 309, the active manager addressesits own request for an action or for obtaining information 310. Apossible request for the active manager is to relinquish themanagementship to another entity in the aggregate as noted at step 311.If such a request has not been placed the active manager, places abroadcast message requesting from all unmapped entities in the aggregateto announce their presence 312. If any response at all is received 313,the active manager performs the aggregate mapping procedure as describedin FIG. 7.

The actions performed by an entity which is not a designated entity aredescribed in FIG. 6. The cycle of activities for a non designated entitybegins by waiting for a message (packet) addressed to it as noted at402. The entity waits for a specified and agreed upon period of time at403. If the said time expires and no message has been received (eitheraddressed to the entity in discussion or not) the entity will attemptone of the following two actions:

1. If the entity can become a designated entity it will try to establishitself as the designated entity at 406.

2. If the entity cannot become designated it will revert to the lastsettings recorded in its P₋₋ Table (i.e. Parameters Table). (For addeddetail see also FIG. 4.)

If any message is received the waiting lime is reset at 404. Thereceived packed is analyzed at 405. The following cases exist:

A "Get" request is received. The unit is requested by the designatedentity to provide information. The entity supplies the information at407.

A "Put" command is received. The command may be a "Sleeping Pill" as perstep 417 that is an acknowledgement from the designated entity that thenon-designated entity in discussion is recorded in the mapping table. Ifno "Put" command is received during the polling cycle the any unit willassume that it was removed from the mapping table.

If the received "Put" command is not a "Sleeping Pill" as at 417, the"Put" procedure is performed at 418. Upon completion of the "Put"procedure the non-designated entity returns to step 402. One exceptionis possible, if the non-designated unit is required to assume thefunctionality of a designated or coordinating unit at 416.

The packet type (message type) as sorted in step 409 can be a"Broadcast":

"Open Bridges"--the entity opens the mapping bridges at 415.

"Listen Down-Stream" as per step 414. The entity enables the Downstreamreceiver on the mapping path 20.

"Listen Up-Stream" as per step 413. The entity enables the Upstreamreceiver on the mapping path 20.

"Who hears the mapping Signal?". If the mapping flag is set at 408, thatis the entity is expecting to be mapped, it monitors the mapping signalexpected from the set direction for a set period of time at 410. Ifduring the set period of time the mapping signal is detected at 411 theentity will provide the information identifying itself following a "Get"procedure at 412 and return to the beginning of the cycle at step 402.If no mapping signal is detected during the set period of time at step411 the entity returns to the beginning of the cycle without performingthe "Get" procedure.

In the context of this invention it is assumed that entities in theaggregate may be of such a type that they cannot become designated. Suchentities will default to non-designated status following the power up.In the case that such units detect the absence of any designated entityin the aggregate they follow the procedure 200 as described in FIG. 4.

FIG. 4 depicts the logical flow chart for a non-managing entity.Specifically, for entities which are not connected to a management agent(and/or do not include a coordinating processor and memory), after thestarting point 100 the entity in a manner described with regard to FIG.3 checks if it has received a transmit request at step 202. If a requesthas been received, a response is sent as noted at step 204. However, ifno request has been received, a time out is taken as noted at step 206.As noted above with regard to the responsibilities of the entitydesignated as the coordinating entity, the designated entity is requiredto address each entity in the aggregate within a specified and agreedupon time period. As noted at step 208, the entity will revert to thelast settings and operate independently if they cannot act as acoordinating entity and if no coordinating entity has been designated.

FIG. 8 shows the concepts of a collision means 60 for detectingcollisions. The collision detection is used by the coordinatingprocessor, particularly the designation means of entities which can actas coordinating entity. The collision means 60 is implemented on thedata path 16 and can be used to detect the transmission of anidentifying message by several entities which have the capability to bedesignated as communications coordinator (as discussed above).

The signals to the data path are driven by a differential line driver 62through a complex impedance "Z" (64). The impedance "Z" can be forexample a 50 Ohm resistor in series with a 0.1 μF capacitor, or theequivalent circuit of a transformer. The two voltage comparitors 66 areconnected to implement a set reset flip-flop. The switching thresholdfor the set-reset flip-flop is determined by the output voltage levels,the values of the resistors R1 and R2 and the V_(ref). The switchingthreshold of the implemented set-reset flip-flop is set to half thevoltage of the transmitted signal into the data path. For example suchsettings may be:

Transmitted signal: 5.0 V±0.5 V differential

Received signal: 2.5 V Minimum.

The data rate of the transmitted signals is such that the maximal sizeof the data path is significantly smaller than the electrical length ofone transmitted bit. Upon simultaneous transmission of signals from twoentities which have the capability of being designated as thecommunications coordinator, due to the fact that each message has aunique content at least some of the time the signals will be of oppositepolarity. Those signals will set on the medium of the data path 16 avoltage level which cannot flip to the receive circuit. Each entity(base unit) which has the capability to be designated as thecommunications coordinator compares the transmitted message with thereceived message, and if the two are not identical it is assumed that acollision occurred. When not transmitting, the differential line driver62 sets its output to high impedance.

FIG. 9 depicts an embodiment of the invention wherein a plurality ofentities 12 are provided in the form of stackable hubs (concentrators)40. Each concentrator 40 has a plurality of ports 24. Some of theconcentrators (at least one) are entities which can be designated ascoordinator. These base unit(s) may be connected to a management agentand include a coordinating processor and memory. Each of the ports 24may be connected to a user such as a computer which is to be connectedto a network via the concentrator. The concentrators are connected via amedium 26 by point-to-point connection 22 in order to provide themapping path 20. Additionally, the concentrators are connected via themedium 26 to provide the data path 16. Different wires may be used forthe paths (spatial multiplexing) preferred or the paths may be formed oncommon wires (or optical guides). The cables 26 connecting the entities(boxes 40 in FIG. 9) contain appropriate elements to implement themapping path. In the implementation given as an example, one pair oftwisted wires is used for point-to-point connections between the boxes40. A second and different pair of twisted wires implements the datapath. After connection of the data path and the mapping path as shown inFIG. 9, a communications coordinator is designated as described herein.After such designation of a communications coordinator, mapping isperformed and subsequently communication on the data path andcommunication on the mapping path proceeds.

Referring to FIG. 10, the preferred form of the invention includes datapath transmit and receive circuitry generally designated 50. Thiscircuitry includes the collision detect means 60 as well as line driver62 U1 (RS 485). Signals which are to be transmitted over the data path16 are generated in a TTL (transistor-transistor-logic) format andpresented to the transmit/receive circuitry 50 at the data input 52.Data Ring A and Data Ring B are the two pins which attach to the datawires 16. While transmitting signals on the data path 16, the outputpins of the processor U1 (75176) are activated by the data₋₋ en input54. If no signal is to be transmitted on the data path 16, the outputpins A and B of chip U1 are set to present a high impedance. The signalsto be transmitted propagate differentially from pins A and B of U1through two identical impedances implemented by C1 (0.1 μF) and R6 (51.1Ω) to pin 9 on U2 and through C4 (0.1 μF) and R7 (51.1 Ω) to pin 5 onU2. U2 is a package containing four comparators 66 commercially namedLM339. Two of the comparators 66 are connected to implement a SET/RESETFLIP/FLOP. That is achieved by the connection of R12 (18 kΩ) between theoutput at pin 2 on U2 and the input at pin 8 on U2, and R13 (18 kΩ)between the output at pin 14 on U2 and the input at pin 4 on U2. Twoadditional resistors R10 and R11 (both 3.9 kΩ) are serially connectedbetween the inputs at pins 8 and 4 on U2 in order to set the switchingthreshold for the implemented SET/RESET FLIP/FLOP. A capacitor C12 (0.1μF) connects to GND the point between R10 and R11 for filteringpurposes. The received signal (DATA₋₋ Received) is presented to otherfunctions inside each entity enclosure in TTL levels through a thirdcomparator 66 in U2 at output 13.

FIG. 11 shows a mapping signal generation and detection circuitgenerally designated 70. The signals on the mapping path 20 aregenerated and detected by two components U4 and U5 (both 75176transmit/receive elements). The mapping signal is generated by a circuitimplemented around one of the four comparators contained in U1. Ahysteresis is created by R19 (47 KΩ), R17 (47 KΩ) and R18 (47 kΩ). Anegative feed-back through R20 (47 KΩ) between pins 1 and 6 on U2 andC13 (1500 pF) establishes an oscillation frequency of 10 kHz±5%. Thesignal is permanently attached to both components U4 and U5 at pins DIN.In order to select which component will actually send the signal thefollowing controls will be set

Listen₋₋ Up/DownStream. This signal is presented to U4 and U5 inopposite polarities. Therefore when U4 is in receive mode U5 will be intransmit mode and conversely when U5 is in receive mode U4 will be intransmit mode.

Transmit₋₋ UpStream. This signal sets the output impedance of U4 to lowvalues and enables the transmission drivers to propagate the signal onthe mapping path 20.

Transmit₋₋ DownStream. This signal sets the output impedance of U5 tolow values and enables the transmission drivers to propagate the signalto the mapping path 20.

Resistors R22 (3.3 kΩ), R23 (3.3 kΩ), R24 (3.3 kΩ), R25 (3.3 kΩ) inconjunction with R26 (220 kΩ), and R27 (220 kΩ), set a convenient biason the inputs in order to prevent triggering of the circuit by noise.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A system for communication and management of anaggregate based on separate entities, comprising:a plurality of separateentities, each entity residing in a separate environment and having nopredefined address for the purpose of communication between saidseparate entities of said aggregate; a data and management path providedas a common medium, each of said entities being connected to said dataand management path for exciting the medium with a signal, all entitiesconnected to said common medium receiving said signal allowingcommunication between said separate entities including the transfer ofdata packets between said separate entities and the transfer ofmanagement data of the aggregate including data for changing and settingoperating parameters of the aggregate and the transfer of data forassigning a unique identifier to the separate entities for acquiringstatistical data; a mapping path implemented as a multitude of point topoint connections such that each entity is connected to an adjacententity via a point-to-point connection and is connected to anotheradjacent entity via a point-to-point connection providing a predefinedtopology, said mapping path for passing mapping signals between adjacententities for locating entities in the aggregate including locating eachentity with respect to said predefined topology; a management agentconnected to said aggregate via one or more active points of accessresiding in one or more of said entities, said management agentincluding a mapping table, said management agent for initiatingidentification via said mapping path including receiving a message fromall unmapped entities and establishing a mapping address for each entitybased on said message and sending data assigning said unique identifierand for mediating the transmission of commands including changing andsetting operating parameters of the aggregate, wherein one or more ofsaid entities are capable of providing a point of access to saidmanagement agent; and designation means for participating in a processfor designating a coordinating entity, each of said one or more of saidentities including designation means, said coordinating entity providingsaid point of access to said management agent for managing andcoordinating communications over said data path, wherein saiddesignation means listens to said data path medium for a predeterminedperiod of time for detection of communication signals, upon detectingcommunication signals said designation means of said entity awaitsissuance of a message, by said coordinating entity, requesting allun-mapped entities to signal their presence, if no communicationsignalling is detected on said data path, said designation meansinitiates an algorithm including transmitting a signal containing uniqueinformation identifying itself, if during transmission of said uniqueinformation identifying itself additional entities transmit their uniqueinformation identifying themselves, said designation means of each ofsaid entities will end their transmission and randomly choose a timeperiod, upon expiration of said randomly chosen time period, saiddesignation means of each entity will attempt to transmit again itsunique information identifying itself, upon the occurrence oftransmission of said unique information identifying itself, saiddesignating means which completed said transmission is established asthe coordinating entity.
 2. A system according to claim 1, wherein saidmanagement agent maintains statistics regarding communication over saiddata and management path based on the stored information.
 3. A systemaccording to claim 1, wherein said coordinating entity is connected tosaid management agent.
 4. A system according to claim 3, wherein saidcoordinating entity coordinates all communications on said data pathincluding sending a message addressed to an entity in said aggregate,whereby the entity after receiving said message from said coordinatingentity performs necessary operations and transmits a message containinginformation relevant to the received message, said coordinating entityaddressing each entity in said aggregate within a specified and agreedupon time period.
 5. A system according to claim 4, wherein eachdesignating means of each entity, upon listening to said data pathmedium for a predetermined period of time and not detecting anycommunication signals;isolates itself whereby said entity operates as astand alone entity independent of said aggregate; initiates saidalgorithm for designating an entity in the aggregate to coordinate thetransfer of information; or awaits for the coordinating entity to issuea message requesting all un-mapped entities to send a message announcingthat they are connected to the aggregate.
 6. A system according to claim1, wherein said mapping path is independent of said data path, allowingtwo entities in said aggregate to communicate simultaneously along saiddata path and along said mapping path.
 7. A system according to claim 6,wherein said predefined topology of said mapping path is a ring, withpoint-to-point contact between adjacent entities.
 8. A system accordingto claim 6, wherein said mapping path is provided on said common medium,implemented by multiplexing data/management signals and mapping signals.9. A system according to claim 8, wherein said multiplexing is one ofspacial multiplexing or multiplexing based on different frequencyranges.
 10. A method for communication and management of an aggregatebased on separate entities, comprising:providing a plurality of separateentities, each entity residing in a separate environment and each entityhaving no predefined address; providing a data and management path as acommon medium; connecting said entities to said data and managementpath; exciting the medium with a signal, for communication, wherein allentities connected to said common medium receive said signal; providinga mapping path implemented as a multitude of point to point connectionssuch that each entity is connected to an entity via a point-to-pointconnection and each entity is connected to another entity via apoint-to-point connection to form a known topology; identifying allentities adjacent to a given entity using said mapping path to establishmapped adjacent entities and from said mapped adjacent entitiesestablishing a unique identifier for each of said entities adjacent tosaid mapped adjacent entities until all entities of the aggregate aremapped and saving said unique identifier; providing a management agent;connecting said management agent to said aggregate via one or moreactive points of access residing in one or more of said entities; andfor initiating identification via said mapping path and storinginformation relating to said identification for managing access to saiddata/management path, and maintaining statistics regarding communicationover said data/management path based on the identification saved;providing one or more of said entities with the capability of providinga point of access to said management agent, providing said one or moreentities with designation means for participating in a process fordesignating a coordinating entity, said coordinating entity providingsaid point of access to said management agent; listening to said datapath medium for a predetermined period of time for detection ofcommunication signals; upon detecting communication signals awaitingissuance of a message, by said coordinating entity, requesting allun-mapped entities to signal their presence; if no communicationsignalling is detected on said data path, initiating an algorithmincluding transmitting a signal containing unique informationidentifying an entity; if during transmission of said unique informationidentifying an entity additional entities transmit their uniqueinformation identifying themselves, ending their transmission andrandomly choosing a time period; upon expiration of said randomly chosentime period, attempting to transmit again the unique informationidentifying the entity; and upon the occurrence of transmission of saidunique information identifying the entity establishing the entity ascoordinating entity.
 11. A method according to claim 10, furthercomprising coordinating all communications on said data path with saidcoordinating entity including sending a message addressed to an entityin said aggregate, whereby the entity after receiving said message fromsaid coordinating entity performs necessary operations and transmits amessage containing information relevant to the received message, saidcoordinating entity addressing each entity in said aggregate within aspecified and agreed upon time period.
 12. A method according to claim11, wherein each designating means of each entity, upon listening tosaid data path medium for a predetermined period of time and notdetecting any communication signals;isolates itself whereby said entityoperates as a stand alone entity independent of said aggregate;initiates said algorithm for designating an entity in the aggregate tocoordinate the transfer of information; or awaits for the coordinatingentity to issue a message requesting all un-mapped entities to send amessage announcing that they are connected to the aggregate.
 13. Asystem for communication and management of an aggregate based onseparate entities, comprising:a plurality of separate entities, eachentity residing in a separate environment and having neither apredefined identity nor a predefined address; a data and management pathprovided as a common medium, each of said entities being connected tosaid data path for exciting the medium with a signal, all entitiesconnected to said common medium receiving said signal allowingcommunication between said separate entities including the transfer ofdata packets between said separate entities and the management of theaggregate including changing and setting operating parameters of theaggregate; a mapping path implemented as a multitude of point to pointconnections such that each entity is connected to an adjacent entity viaa point-to-point connection and is connected to another adjacent entityvia a point-to-point connection; and a management agent connected tosaid aggregate via one or more active points of access residing in oneor more of said entities, said management agent for controlling mappingsignals over said mapping path to determine the existence of each unitand identify the position of each unit relative to the aggregate forproviding a unique identifier to each of the separate entities, based ona known topology and saving said unique identifier in a mapping table,wherein said managing agent uses a distributed algorithm means forimplementing an algorithm for mapping the entities, each of saidentities including a mapping bridge, which, according to settings ofsaid mapping bridge, propagates said mapping signal from a precursorentity to a succeeding entity, upon propagating said signal, saidalgorithm means assigning said succeeding entity a unique identifier, ifsaid succeeding entity has not been assigned a unique identifier, saidalgorithm means repeatedly implementing said algorithm until allavailable paths of a predefined topology receive said mapping signal.14. A system according to claim 13, wherein said managing agent uses adistributed algorithm means for implementing an algorithm for mappingthe entities, each of said entities including a mapping bridge which,according to settings of said mapping bridge, propagates said mappingsignal from a precursor entity to a succeeding entity, upon propagatingsaid signal, said algorithm meansassigning said succeeding entity aunique identifier, if said succeeding entity has not been assigned aunique identifier, said algorithm means repeatedly implementing saidalgorithm until all available paths of a predefined topology receivesaid mapping signal.
 15. A system according to claim 13, wherein saidmanagement agent checks all paths of said predefined topology for areturn of said mapping signal for stopping implementation of saidalgorithm and if said predefined topology does not allow a return ofsaid mapping signal to said managing agent, said mapping agent sets allmapping bridges along all available paths until a set time has passedindicating said mapping path is not able to return said mapping signalto said management agent.
 16. A method for communication and managementof an aggregate based on separate entities, comprising:providing aplurality of separate entities, each entity residing in a separateenvironment and each entity having no predefined address; providing adata and management path as a common medium; connecting said entities tosaid data and management path; exciting the medium with a signal, forcommunication, wherein all entities connected to said common mediumreceive said signal; providing a mapping path implemented as a multitudeof point to point connections such that each entity is connected to anentity via a point-to-point connection and each entity is connected toanother entity via a point-to-point connection to form a known topology;identifying all entities adjacent to a given entity using said mappingpath to establish mapped adjacent entities and from said mapped adjacententities establishing a unique identifier for each of said entitiesadjacent to said mapped adjacent entities until all entities of theaggregate are mapped and saving said unique identifier; providing amanaging agent; and using a distributed algorithm means by the managingagent for mapping the entities, each of said entities including amapping bridge for opening one or more of said point-to-pointconnections, said distributed algorithm for:designating one of saidpoint-to-point connections of each entity as an upstream connection,opening said mapping bridge to prevent a mapping signal from propagatingalong the mapping path, listen to an upstream connection on the mappingpath, and transmitting a mapping signal in a downstream direction,opposite said upstream direction, waiting for a mapping signal from theupstream direction and if no signal is received, requesting identifyinginformation as to the entity in the aggregate which has received themapping signal and upon reception of identifying information, savinginformation in a mapping database to establish said unique identifier.